“What did he seem to want in Mother Flintstone’s old quarters?” “I hardly know. He sounded several of the walls, as if looking for a secret door, but he didn’t appear to find one.” “Anything else?” “He went over the floor like a fox, with his nose close to the boards.” “Was that all?” “No, he even sounded the ceiling.” “Quite particular,” smiled the detective. “Wasn’t he, though? I never saw anything just like that. He didn’t let an inch of space escape him.” “Did he seem excited?” “Not a bit of it. He was as cool as a cucumber, and not for a minute did he get off his base. He seemed disappointed, though, that’s all--as if he expected to find some hidden wealth and didn’t, you see.” “Maybe he overlooked it, Billy.” “I don’t think there was any to overlook,” said the boy. “But, really, there’s no telling what that man was huntin’, but he wasn’t thar for any good you can bet your neck, Mr. Carter.” “I’ll agree with you on that score, boy,” and the detective put the card in his pocket. “George Richmond never goes out after small game. That’s his record.” “Do you think he had anything to do with the murder of Mother Flintstone?” eagerly questioned the boy. “Time will tell,” was the detective’s reply. “Do you think he had, Billy?” “I do, I do,” cried the boy. “Bless me if I kin get the idea out o’ my head. That man either killed Mother Flintstone or he knows who did.” To this the detective made no reply, and he told the boy to go back to bed. “Have you struck any clew yet, Mr. Carter?” asked Billy. “A little one. There, go to bed and let me go to work again.” “I will, but keep an eye on the man I saw to-night in Mother Flintstone’s house. He needs watchin’ day and night. Good night, Mr. Carter.” Five minutes later the famous detective was far from Billy’s uncouth abode, and in an entirely different part of the city. He stopped at last, and looked up at a tall building that seemed to cleave the darkened sky far overhead. The brief inspection seemed to satisfy him, for he entered the main hallway and began to climb the uncarpeted stair. He reached the third floor before he encountered any one, and there he was suddenly brought to a halt by a voice that rang down the ghostly corridor. “Another step on your life! I have you at my mercy and I never fail to bring down my man. Stand where you are, for another step means a bullet in your brain!” CHAPTER XXII. THE BIRD IN THE DEATH TRAP. Leaving Carter, the shadow, in the net of doom, let us go back a little in our story of crime and see how fared one of our other characters. You will recollect Margie Marne’s visit to the Trocadero in answer to the mysterious note which had reached her, and how the detective discovered that the person whom she encountered vanished with her into the alley back of the café while the detective himself was coolly and cleverly drugged by Caddy.